Usage of C# packages from F# is simple and without issues. The other way is a bit more clunky, but frankly, you will not want to write any C# once you are on the F# side.
I have been programming in F# full time for the past 7 years and I hope that rumours of its death are greatly exaggerated. Perhaps this comes from a point of view that if something is not growing 10x each year is dead?
It's not a JavaScript framework that has an average lifespan of a couple of years. It's a fully featured, complete, very productive language that makes programmers life easier and more enjoyable.
